Lawn Diseases How to Prevent And Control Them Effectively

Lawn Diseases Lawn Diseases How to Prevent And Control Them Effectively

lawn diseases
Lawn diseases are the most difficult type of lawn pest to identify and control because they are commonly misdiagnosed as insect pests damage or are not treated with the correct fungicide. Yes lawn fungus are classified as a disease pest therefore fungicides and bactericides are classified as pesticides.

WARNING this article is for those who want a great looking lawn!

Lawn diseases need three basic needs to cause damage.

1. The pathogen bacteria or fungi needs to be present
2. The right host or plant, lawn variety must be present
3. The right environmental conditions temperature, water, must be present.

When all these three become available the bacterial, fungi or pathogen can become active and cause damage to the host plant or lawn variety.

To help prevent lawn diseases the right cultural practices must be applied to reduce the susceptibility of lawn fungus.

For those lawn fanatics that want a perfect lawn this is what’s required to achieve your goal of a perfect lawn. The rest will experience mediocre results.

In my over 10 years of experience I have found 3 common practices that lead to lawn diseases and they have nothing to do with pesticides.

Proper Mowing helps prevent lawn disease

The right mowing height and frequency for the cultivar of lawn that is different for every type of lawn, However there proven principals that work for every type of lawn.

Never allow lawns to grow longer than it would take to remove no more than 1/3 of the leaf blade. Removing more than 33% of the leaf blade will cause stress by removing stored food supply and make you lawn more susceptible to lawn disease, if you allow it to grow to long further than the 1/3 rule, because you cant have it mowed more often either because of time or or both then this will cause rotting because the the right amount of light cannot penetrate.

Don’t commit the fatal mistake of mowing your lawn really short so you don’t have to mow it as often. This is a practice known as scalping and it is the number 1 contributor of a hideous lawn and lawn diseases.

If you prefer a short lawn you need to a lawn that is designed for short mowing.

Here is the harsh reality! Your lawn doesn’t care about your schedule, budget, thoughts or feelings all your it wants what it wants when and how it wants it.

You either treat it like it wants to be treated or it will not thrive.

Example: If your variety requires to be cut at 3 inches in height never allow it to grow past 4.5 inches in height.

Make sure you mower blade is sharp all the time, a dull mower blade will shred the leaf blade and create open wounds where pathogens can enter, not only that but created a stressed leaf blade with a weakened defense system more susceptible to lawn diseases.

Proper Watering to prevent lawn disease

The right amount of water, frequency and timing. Avoid watering at in the evening, lawns which are watered in the evening will experience more frequent lawn diseases because was wet all night with lower temperatures, its like having your foot in a wet boot all day your going to get an infection.

Water first thing in the morning between 4 am and 6 am, so by sunrise the sun will burn off the excess water on the leaf blade and reduce the susceptibility of lawn diseases.

Length of watering to prevent lawn diseases

Proper watering length of time is important soil type, temperature, rain and drainage are things you need to consider in order to properly your lawn the front of your homes lawn may drain faster than the lawn in the back or sides of your home.

A cheep tool to use is a soil moisture tester you can pick up for $5 to $15 at many home improvement stores. With it you can test the soil in front, sides and back of your home or property to see how much water is in the soil and adjust your irrigation accordingly.

Frequency of watering prevents lawn diseases

Frequency is the number of days per week you will need to water your lawn, some cities around the country have water restrictions so you may be restricted on how many days per week you can water your lawn. But unless you have a zero water restriction you can train your lawn to the minimum water usage possible.

For most properties twice a week is suffice, but you may require more or less, only monitoring your lawn can tell you the right amount.

But one thing is for sure more damage is caused to lawn by over watering than under watering.

Proper Lawn Fertilizing helps prevent lawn diseases

Fertilizer can be a double edge sword to much fertilizing and you may increases fungal disease susceptibility, too little fertilizing and your lawn becomes susceptible to lawn diseases.

So proper nutrition is vital for reducing susceptibility of lawn diseases.
There is no general guideline for how much nitrogen, phosphorus or potassium in addition to micro nutrients such as manganese, magnesium or iron to add to a lawn.

Fertilizer restriction laws

Fertilizer laws are different all over the US and the world, many states, counties and municipalities have or are imposing fertilizer restrictions.

Different varieties will require different amounts of nutrients, your best bet is to contact you state or county extension to find out which fertilizer is best for your type of lawn with your type of soil in your area.

Bellow are some great links to help you identify and manage lawn diseases.

Lawn disease identification tool

Bellow are 2 lawn diseases identification tool

You simply select the lawn type
Select the month of the year you are having the problem and it will tell you the type lawn diseases you may have.
Then you can do your research

Lawn Diseases

Lawn Diseases Management

Rhizoctonia Blight

Rhizoctonia Blight is also known as Brown Patch, Large Patch, Yellow Patch

Pathogens: Rhizoctonia solani and R. cerealis

Rhizoctonia lawn diseases are more severe under conditions of poor drainage, high compaction, thick thatch layers, long periods of leaf wetness, low mowing heights, excessive mechanical damage, and high nitrogen fertilization.

Large patch on Bermudagrass, zoysiagrass, St. Augustinegrass, kikuyugrass lawn disease develops in fall and spring when warm season grasses are going in or out of dormancy.

Brown patch: bentgrasses, fescues, ryegrasses, bluegrasses is common when temperatures are in the range of 75° to 95°F, with the optimal conditions for leaf being temperatures of 85° to 90°F with high humidity or extended leaf blade wetness periods.

Yellow patch usually on annual bluegrass, Kentucky bluegrass, bermudagrass, perennial ryegrass, zoysiagrass, bentgrasses lawn disease develops when air temperatures range from 50° to 65°F and where there is high humidity and or extended periods of leaf blade wetness. In most cases, the turf grass will recover when temperatures go above or below this range.

Pyricularia grisea

Gray leaf spot is a disease caused by the fungus Pyricularia grisea, also known as Magnaporthe grisea and is considered a fungal disease primarily perennial ryegrass and St. Augustine grass. The disease first appears as tiny brown spots that enlarge and become oval or elongated. The mature spots usually have depressed gray centers with irregular brown margins, and a ring of chlorotic tissue surrounding. Severe infection shows burned or scorched blades of turfgrass. Lesions are also found on the leaf sheath, spike and stems. Stem lesions tend to be brown to black.

The disease is most severe during humid, warm weather, frequent warm rainy periods create a perfect condition for gray leaf spot fungal disease, high humidity and high temperature (80° to 90° F) the disease may develop rapidly the spores are spread by wind and water to other healthy lawn.

Newly installed St. Augustine grass is more susceptible to gray leaf spot than established older mature turfs.

Gaeumannomyces graminis var. graminis

Take all patch Take-all Root Rot
Pathogen: Gaeumannomyces graminis var. graminis

Take all patch or take all root rot is associated with a root decline of bermudagrass, centipedegrass, and St. Augustinegrass in the southeastern United States.

Gaeumannomyces graminis is a necrotrophic soilborne pathogen that lives in the soil and the root and crown tissue of many members of the grass family.

In Bermuda grass it is known as Bermuda grass decline, take-all root rot of St. Augustine grasses and take all patch in creeping bentgrass.

Soil conditions that favor this fungal disease includes low organic matter, high sand content, low fertility, pH levels above 6.5, and high soil moisture, temperatures that drop bellow 65 F. Changing cultural practices can aid in alleviating disease occurrence and severity.

Panicum mosaic virus

Mosaic disease of St. Augustinegrass infected with Sugarcane Mosaic Virus or St. Augustine decline (SAD)

Pathogen: Panicum mosaic virus

Fungicides are ineffective and cannot stop development or spread of this viral disease.

Sugarcane Mosaic Virus can be efficiently transmitted by mechanical means. Line trimmers, and other equipment can transfer clippings and sap containing virus from lawn to lawn. Aphids are also known to transmit the virus as well, however it is not known how important aphids or other potential insect transmit disease spread. The virus also can be spread on infected sod during the times of year when symptoms are mild and not obvious. Sod with Sugarcane Mosaic Virus should not be used.

The most severe symptoms in this recent epidemic have been found on ‘Floratam’ St. Augustinegrass. ‘Floratam’ sod used to replace lawns that died from mosaic has died again in many cases. ‘Palmetto’ and ‘Bitterblue’ may get the disease but are more resistant. the virus has been reported to infect grasses bermudagrass, seashore paspalum and bahaiagrass, ornamental fountaingrasses and St. Augustinegrass. Mosaic is currently a concern on St. Augustine grass in Florida.

Cercospora fusimaculans

Cercospora Leaf Spot
Pathogen: Cercospora fusimaculans also known as Passalora fusimaculans
Turfgrasses Affected: St. Augustinegrass

Cercospora Leaf Spot appears between the late spring and summer seasons, especially during periods of frequent rainfall. St. Augustinegrass that is under cultural or environmental stresses are more susceptible to disease development. Low soil fertility or bad light conditions are conducive to the development of Cercospora Leaf Spot

Currently there is no chemical control available.

Proper cultural control practices are the key reduce the risk of Cercospora leaf spot disease. The disease can be prevented by fertilizing adequately, using slow-release nitrogen sources balanced with potassium .

The irrigation cycle should be for proper timing, frequency, and amount. Lawns should only be Irrigated in the early morning hours between 5:00 and 8:00 a.m. when the dew is already present so as not to extend the dew period.

Turfgrass should only be irrigated when it exhibits moisture stress. Daily or frequent irrigation can foliar disease and should be avoided.

If Cercospora leaf spot is present, the disease can be managed by making an application of quick-release nitrogen in a fertilizer blend balanced with potassium (N:K ratio of 1:1).

The fertilizer can be applied at 1/2 lb Nitrogen per 1000 sq ft and should be ammonium nitrate, ammonium sulfate, or quick-release urea nitrogen.

Puccinia spp.

Rust Pathogen: Puccinia spp.

Turfgrasses Affected: St. Augustinegrass and zoysiagrass can be affected, but it may also be observed on perennial ryegrass used to overseed lawns in the winter months.

Rust disease can occur from late fall to early spring when the turfgrass growth is slowed as a result of cool weather. In most cases the disease disappears as soon as the weather warms and the turfgrass starts to grow vigorously again.

It is more severe on turfgrass areas that are stressed from nutrient deficiencies or shade such as under trees or on the north side of a building. It is vital to maintain a balanced fertility program using slow-release nutrient sources.

Leaves must be wet for rust infection to occur. This wetness may be from dew, high humidity, rain, or irrigation avoid irrigating at night. In shaded areas, irrigation should be monitored closely to keep the leaves as dry as possible.

People ask me all the time what is the best or strongest fungicide for my lawn disease? That is like asking your doctor which is the best antibiotic.

The key is to first correct the cultural practices to prevent or minimize the susceptibility of lawn diseases and the the use of fungicides.

Second correctly identify lawn diseases to make sure its not insects that is causing the problem.

If know you have lawn diseases then these 2 fungicides can solve your problem. But understand that fungus bacteria are biological meaning they are living and do mutate, and become resistant to fungicides the same way bacteria in humans become resistant to antibiotics and your Dr. may have to change your prescription to another antibiotic in order to get a cure.

Second lawn diseases are not cured in the sense that if you apply a fungicide you will not have it again, fungicides control or suppress the fungus.

The reality is if you have a lawn diseases in your lawn you will have it again and usually at the same time next year in the same place, this is because most bacteria are soil borne meaning they live in your soil and the pathogens can be latent or asleep and the right conditions will make them active.

Bellow are 2 fungicides I use on our customers lawns, you have a link to a resource where you can purchase them online with free shipping, also you can get labels and msds.

Heritage Active ingredient Azoxystrobin 50%

heritage fungicide

Heritage is a newer class of fungicide belonging to the systemic class of fungicides, penetrating the leaf and vascular system through the roots allowing control of leaf, crown and root disease control, giving you complete control of lawn diseases with as little as one application at the lowest label rate.

Heritage is very portable it comes in a wettable granule in 4 oz or 16 oz container with a measuring cup that is easy to use.

Heritage can be applied with a hand held or backpack sprayer so you don’t need any special equipment because of this you can apply it with very little water.

Second is

Eagle Fungicide Active Ingredient Myclobutanil 19.7% 

Eagle fungicide

Eagle also belongs to the systemic class of fungicides so it is very good at controlling lawn disease in leaf blade, root and crown.

Eagle comes in a liquid concentrate with its own measuring device right on the bottle so it makes it very easy to use.


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